The technology described herein relates to data processing systems and in particular to a method of and apparatus for the protected processing of protected content by an accelerator, such as a graphics processing unit (GPU) or a video decoder, under the control of a non-trusted (non-secure) operating system (OS).
Many electronic devices, such as mobile phones or tablets, for example, will include both a host processor (CPU) that executes an operating system, such as Android, and one or more accelerators, such as a GPU, that provide hardware support for specific functions. In the case of a mobile phone or tablet, for example, the GPU may be used to generate the user interface that is displayed under the control of the operating system, and to compose the frame that is displayed on the display to the user.
It is becoming increasingly common for content providers to wish to provide (e.g. stream) protected content, such as videos, to electronic devices (and in particular to mobile devices). In order to support this, it is necessary for the electronic devices to be able to ensure the security of the protected content when it is, e.g., being played back to a user via the device.
One way to do this would be to provide a secure operating mode and environment for the electronic device in which the security of the protected content is protected. For example a protected video player on the electronic device could be used to playback protected video content in a secure fashion, with a 2D composition engine being used directly by the protected video player to provide secure full-screen playback of the protected video content.
However, if the operating system user interface is then needed to be displayed (e.g. to provide notification of an incoming call, text message received, email received, etc.), then the display composition would normally need to switch to the GPU that is generating the user interface. However, current secure video solutions on mobile devices, such as mobile phones, can't perform GPU display compositing in combination with secure video playback. This will then normally require the video playback to be suspended, in order to maintain the protection for the protected video content.
The Applicants believe therefore that there remains scope for improved mechanisms for the provision of protected content processing on electronic devices.
Like reference numerals are used for like features throughout the drawings where appropriate.